Numerous products, such as soft drinks and beer, are packaged in containers under pressure. The pressure under which these products are packaged results from the carbonation within the product, i.e., the sealed container is pressurized due to the nature of the product within the container.
Some containers, notably two-piece aluminum and steel cans, are designed with the minimum side wall thickness possible, to reduce the amount of metal required to form the container and thus to reduce the cost of the container. These containers, as well as such other containers as plastic bottles and the like, rely heavily upon the internal pressure of the product within the container to increase the burst strength and overall wall strength of the container.
Whether the carbonated products be packaged within a can, bottle or other container, air is removed from the headspace above the product in the container prior to sealing of the closure onto the container, due to the carbon dioxide released by the product. Removal of this air from the headspace above the product within the container is desired to help prevent spoilage of the product due to air.
Recently, it has become increasingly popular to package non-carbonated products, such as fruit drinks and the like, in the same containers which have been employed in the past only for carbonated products. However, since these products are still, i.e., they do not develop internal pressure due to carbonation after sealing of the container, these products cannot be relied upon to add structural strength to a filled metallic container, plastic bottle, and other similar containers, nor can these products be relied upon to remove air from the headspace above the product prior to sealing of the container by means of a closure element.
It is known to physically mix gaseous nitrogen into such still products prior to packaging thereof, in order to provide nitrogen gas for both pressurization of the container and to remove air from the headspace above the container just prior to sealing. However, nitrogen gas does not mix easily with these products, and thus this process is a rather time consuming and expensive one.
It is also known from British Pat. No. 1,455,652 that container bodies filled with still products could be pressurized by placing drops of liquid nitrogen or a liquified noble gas into the filled container, followed by immediate sealing of the container. After sealing, the evaporating liquified gas, now in its gaseous form, would pressurize the container body.
Unfortunately, the British patent illustrates no complete apparatus for accomplishing this result. One apparatus for accomplishing this result was proposed in U.S. application Ser. No. 38,011, filed May 10, 1979, now abandoned. Control of the liquified gas level was difficult in this apparatus, and freeze-up, due to moisture entering the apparatus, was a continual problem.